Process for production of propellant charges comprising compressing geometrically shaped powders together

ABSTRACT

A PROCESS FOR PRODUCING SHAPED POWDER ARTICLES FOR PROPELLENT CHARGES BY PRESSING POROUS POWDER GRAINS HAVING EXTERNAL GEOMETRIC SHAPES EXHIBITING EDGES, SPIKES OR THE LIKE WHICH PERMIT THE GRAINS TO INTERLOCK WITH EACH OTHER. PREFERABLY THE GRAINS HAVE T, X, Y, OR V-SHAPES, ALSO DSCLOSED ARE SHAPED POWDER ARTICLES PRODUCED BY THIS PROCESS.

United States Patent m 3,754,060 PROCESS FOR PRODUCTION OF PROPELLANTCHARGES COMPRISING COMPRESSING GEO- METRICALLY SHAPED POWDERS TOGETHERHeinz Gawlick, Furth, Bavaria, and Giinther Marondel, Erlaugen, Germany,assignors to Dynamit Nobel Aktiengesellschaft, Germany No Drawing. FiledAug. 2, 1971, Ser. No. 168,370 Claims priority, application Germany,Aug. 1, 1970, P 20 38 288.1 Int. Cl. C0611 21/02 US. Cl. 264-3 C 11Claims ABSTRACT OF THE DISCLOSURE A process for producing shaped powderarticles for propellant charges by pressing porous powder grains havingexternal geometric shapes exhibiting edges, spikes or the like whichpermit the grains to interlock with each other. Preferably the grainshave T, X, Y, or V-shapes. Also disclosed are shaped powder articlesproduced by this process.

The present invention deals with shaped powder articles and a processfor making the same for use as propellant charges, wherein no solvent orbinder is utilized.

It is conventional to manufacture formed powder articles for propellantcharges by mixing the grains of the propellant powder with a suitablesolvent or a binder, and then pressing the mixture into the desiredshape. During the pressing step, an inherently cohesive body of powderis then produced. This process, however, exhibits disadvantages. Whensolvents are used, the latter can be driven out of the pressed articlesonly with difiiculty. Moreover, the necessary drying procedureinherently changes the geometric configuration so that the desired exactdimensions of the pressed articles cannot be attained with certainty.The use of adhesives undesirably inhibits the deflagration of the powderbody, whereby a non-uniform burning generally occurs leavingnon-combusted residues.

A process for the production of shaped powder articles for propellantcharges by compressing powder grains has now been found which ischaracterized in that porous powder grains are used in the pressing stepwhich exhibit a bulky, geometric configuration interlocking on the outerends (exterior).

It was surprisingly discovered that, when such powder grains are pressedtogether, shaped bodiesare obtained which exhibit the same mechanicalstrength as shaped powder articles pressed with the aid of solvents orbinders, but which do not have the above-mentioned disadvantages.

Powder grains exhibiting the above-disclosed bulky configurations arealready known. They can consist of singleor multiple-base, conventionalpropellant powders. However, preferably, they consist of purenitrocellulose powder because of its variable porosity. It is alsopossible to use, as other components of the propellant powder grains,different explosives or mixtures of these substances which areslow-burning or react under deflagration without tending to detonate,such as, for example, polyvinyl nitrate, nitroguanidine, or penthrite.The powder grains to be pressed should, in this connection possess, ifpossible, the maximum density prior to the pressing step.

The geometric form of the powder grains must be fashioned so that theyexhibit on the surface several pro- 3,754,060 Patented Aug. 21, 1973jecting arms or spikes (tips, points, etc.), so that a projecting arm ora spike of one powder grain engages in the interstices between two armsor spikes of another grain. Grain configurations meeting theseconditions most advantageously are the T-shape, X-shape, Y-shape, orV-shape.

The powder grains must be porous prior to pressing. The porosity isextensively determined by the desired burning velocity and the geometryof the powder grain.

The pressing of the powder grains to form caseless propellant charges isconducted in a conventional manner. Due to the angular configuration ofthe individual grains, the pressure employed in the processing step neednot be excessively high to produce a mechanically strong shaped article.Even at a pressure of 400-500 kp./cm. firm shaped articles are obtained.Advantageously pressures of between 1600 and 5000 kp./cm. are used forthe pressing process.

Due to the fact that the pressure during the pressing step is notexcessively high, the porosity of the individual powder grain ispartially preserved in the finshed shaped powder article.

An additional advantage is that the shaped powder article can again beseparated into the powder grains from which is was produced, during theignition process. Thereby, the burning characteristic of the originalpowder grain is obtained with uniform burning.

EXAMPLE By means of a hydraulic press, tablets 2.5-30.0 mm. in thicknesswere pressed from a propellant powder in a pressing die at a pressure of4000 kp./cm. The propellant powder exhibited the following properties:Individual powder grains were porous exhibiting an angular shape,similar to a V- or Y-configuration. The powder was about 98%nitrocellulose with an N-content of 13.1%.

The strength of the thus-pressed tablets was determined by using atesting arrangement consisting of two planarparallel plates having analmost frictionless parallel guidance.

The pressed article is placed, on edge, between the plates, and one ofthe plates is burdened by weights disposed thereon until the pressedarticle is broken. The value of the weights employed is indicative ofthe strength of the pressed article.

The pressed bodies produced according to the abovernentionedexampleexhibited a strength ranging between 4.0 and 11.0 kp., dependingon the configuration and size of the grain.

It is understood that the embodiments disclosed herein are susceptibleto numerous changes and modifications, as will be apparent to a personskilled in the art. Accordingly, the present invention is not limited tothe details shown and described herein but intended to cover any suchchanges and modifications within the scope of the invention.

We claim:

1. A process for the production of shaped powder articles for propellantcharges comprising pressing together propellant powder grains fashionedto have external geometric angular shapes exhibiting projecting arms orspikes so that the arms or spikes of said angular-shaped grainsinterlock with each other.

2. The process of claim 1 wherein said powder grains are porous.

3. The process of claim 2 wherein said powder grains comprise drypropellant powders.

4. The process of claim 3 wherein said powder grains comprisenitrocellulose.

5. The process of claim 3 wherein said dry propellant powders compriseat least one substance which is slowburning or reacts under deflagrationwithout tending to detonate.

6. The process of claim 5 wherein said at least one substance ispolyvinyl nitrate, nitroguanidine, penthrite, 10

10. The process of claim 9 wherein said pressure is between about 1600and 5000 kp./cm.

11. The process of claim 2 wherein said powder grains exhibit at leastone configuration selected from the group of T, X, Y, or V-shapes.

References Cited UNITED STATES PATENTS 7/1962 Grubaugh 264-3 C 6/1968Nix et al. 1492 X STEPHEN J. LECHERT, 111., Primary Eaminer US. Cl. X.R.

